Systems have been used to allow an implement to be converted quickly and conveniently between a field use position and a transport position for road travel without requiring the operator to install or remove pins or bolts or the like. Some planters have used a combination of an upright central post about which the toolbar and row units are rotated to convert between transport and field use. In this planter, a roller and track set that is engaged through a predetermined vertical distance when raising the toolbar, and then disengages to allow the toolbar to be rotated 90 degrees for rotation to a transport position. One such design is disclosed in U.S. Pat. No. 5,346,019. This design requires that the hitch and main axle of the machine remain at a constant elevation and be of substantial (and thus expensive) construction so that the planter frame and row units can be lifted away from the hitch repeatedly as the planter is raised for turning at the end of the field in preparation for the next planting pass.
This arrangement requires that the support frame for the toolbar and row units be a structure of considerable mass positioned relatively close to the ground. This support structure cannot be raised should it become necessary to cross over a berm or pass through a low lying passage, or encounter other obstructions in the field. Thus, when an obstruction is encountered, the planter hitch and main axle structure are normally dragged across the obstruction. Another drawback of this design is that the guide tracks located on the ends of the axles, which are used to guide and control the toolbar as it is raised for turns at row ends, must be of sufficient height and design that complete engagement is effected through the lift cycle until just prior to the transport height. This results in complications to the overall implement design to incorporate the guide track.
A further characteristic of the prior design is that the same hydraulic cylinders that lift the planter in the repeated field raise/lower sequence are also used to elevate the planter to its road transport elevation.
While this prior design is well-proven and reliable, one potential drawback of the design is that the support wheels at the distal ends of the toolbar are operated by slave cylinders in a master/slave set.
Thus, as the planter is raised to a transport height, the wing wheel cylinders are extended, and left in an extended position, which leaves the wing wheels in a lowered position (relative to the mounting bar of the toolbar). This places the end wheels lower, that is, closer to the ground.
Then, when the toolbar is rotated 90 degrees for transport, the lower end wheels are moved to a position which is transverse to the direction of travel and thus can become damaged by dragging on the ground during transport, if the planter is pulled through a valley or over other abruptly changing terrain.
There are methods using a combination of valves to reverse the flow of hydraulic fluid to the slave cylinders that would cause them to retract as the planter toolbar is raised to the transport position. While this is possible it would complicate the control system and add cost. The instant invention addresses these drawbacks without losing the advantages of a center-rotation/endwise-transport planter design.